SensaPath ultrasonic sensor modules arranged around a wearable headpiece

Embedded system

SensaPath: 360 Proximity Awareness System for the Visually Impaired

A functional wearable prototype that combines five ultrasonic sensing zones, directional vibration feedback, and spoken distance cues around an RP2040 controller.

Overview

Directional awareness without relying on vision

SensaPath explores a wearable way to communicate nearby obstacle movement. Five AJ-SR04M ultrasonic modules cover separate directions around the user. Each zone maps to a coin vibration motor, allowing the feedback location to communicate where an obstacle is approaching.

The front sensor also drives spoken distance feedback through two compact speakers. The prototype integrates sensing, haptics, audio, battery power, a custom PCB, and printed enclosures into one system.

Firmware

Event-driven control on both RP2040 cores

Core 0 manages sensor acquisition, filtering, timeout recovery, and motor policy. Core 1 waits for audio commands and streams stored speech samples through an interrupt-driven PWM output.

Non-blocking trigger, echo, timeout, and cooldown state machine
Sequential acquisition to reduce sensor crosstalk
Fixed-memory data paths with no dynamic allocation
Compile-time UART and USB diagnostic logging
Raspberry Pi Pico SDK, CMake, and C11

Hardware

Integrated sensing, feedback, and portable power

ControllerRaspberry Pi Pico / RP2040
Sensing5 AJ-SR04M ultrasonic modules
Haptics5 coin vibration motors, 10 mm x 2 mm
Audio2 Gikfun round micro speakers
PowerLithium battery and TP4056 charger
Regulation5 V DC-DC boost converter
InterconnectCustom two-layer PCB
PackagingCustom printed sensor and electronics mounts

Electronics design

From schematic to assembled prototype

The custom board centralizes the Pico, five sensor interfaces, five motor outputs, audio path, charger, and 5 V supply within a compact enclosure footprint.

Complete SensaPath electronics schematic — System schematic covering sensing, motor, audio, charging, and regulated power.

Two-layer SensaPath PCB layout — Two-layer PCB layout with the controller, power modules, and channel interfaces.

Assembled SensaPath PCB with Raspberry Pi Pico and power modules — Assembled board during full-system integration and functional testing.

Mechanical integration

Wearable housings designed around the electronics

I collaborated with two mechanical engineering teammates as they designed the printed sensor modules, speaker holder, and main electronics enclosure around wiring, service access, and the wearable arrangement.

CAD views of a SensaPath ultrasonic sensor enclosure — Ultrasonic module enclosure and mounting geometry.

CAD model of the SensaPath speaker holder — Compact speaker holder for audio feedback near the user.

CAD views of the SensaPath battery and controller enclosure — Main enclosure for the PCB, Pico, battery, charger, and boost converter.

Team contributions

My work: firmware and electronics

I authored the full embedded codebase and designed the complete electrical system and PCB. I also led electronic integration, bring-up, and functional testing.

Collaborative work: mechanical integration

Two mechanical engineering teammates led the printed-part design, component ordering, fabrication, and soldering support. We collaborated on enclosure and mounting decisions to align the mechanical design with the electronics.

Explore the firmware

Review the C source, pin assignments, firmware architecture, and Pico SDK build instructions on GitHub.

Open 360System on GitHub